a-a a-b aaa aab aah aao aas ab- aba abb abh abo abs aha ahb ahh aho ahs aoa aob aoh aoo aos as- asa asb ash aso ass baa bab bah bao bas bba bbb bbh bbo bbs bha bhb bhh bho bhs boa bob boh boo bos bsa bsb bsh bso bss haa hab hah hao has hba hbb hbh hbo hbs hha hhb hhh hho hhs hoa hob hoh hoo hos hsa hsb hsh hss oaa oab oah oao oas ob- oba obb obh obo obs oha ohh oho ohs oo- ooa oob ooh ooo oos os- osa osb osh oso oss saa sab sah sao sas sba sbb sbh sbo sbs sh- sha shb shh sho shs soa sob soh soo sos ss- ssa ssb ssh sso sss